Our goal is the continued development of our systematic approach to the chemical synthesis of oligosaccharides. We have devised syntheses of the "building blocks" for oligosaccharides having the general structure D-Gal rho (alpha/beta, 1 yields) (L-Fuc rho (alpha),1 yields)) (D-Gal rho (beta,1 yields) D-GlcNac rho beta, 1 yields)D-Gal, and have made a tetrasaccharide incorporating these features, except for the reducing terminal galactose. We expect to prepare several additional tri-, tetra-, and pentasaccharides of this series. These compounds will be segments of the human blood group B (and I) determinant, or isomers thereof. Work on the synthesis of N-acetyl-D-galactosamine derivatives is in progress, and will be continued. Some of these derivatives are to serve as ligands for the affinity chromatography of galactosamine-binding proteins. Others are designed as precursors of D-galactosamine units in oligosaccharides.